Plastic composition and method of preparing same

ABSTRACT

An improved plastic composition formed by the reaction of an alkenyl aromatic monomer, an acrylic monomer and an interpolymer of ethylene, at least one other straight chain alpha-monoolefin and a compound selected from the group consisting of aliphatic and cycloaliphatic polyene compounds in the presence of a free radical catalyst in an organic solvent, and in the presence of a seed mixture comprising a mixture of said monomers and said interpolymer which has been reacted to at least 15 percent conversion based on said monomers.

D United States Patent [151 3,671,608 Meredith et al. 1 June 20, 1972[54] PLASTIC COMPOSITION AND 3,432,577 3/1969 Serniuk ..260/879 METHODOF PREPARING SANIE 3,435,096 3/ 1969 Limbert et a1. 260/878 3,449,471 669 t2 1. [72] Inventors: Curtis L. Meredith; George A. Von Bodun- 3 483273 3} 2: H bmh Rwge 3,489,821 1/1970 win et al ..260/878 [73] Assignee:Copolymer Rubber & Chemical Corpora- 3,538,191 11/1970 Meredith et al...260/878 tion, Baton Rouge, La.

. Primary Examiner-Harry Wong, Jr. [22] Flled' Nov. 1969Attorney-McDougall, Hersh & Scott [21] Appl. No.: 878,874

[57] ABSTRACT US. Cl. R, An improved plastic composition formed thereaction of an [5 [I'll- Cll r alkeny] aromatic monomer an acrylicmonomer and an inter. [58] Field of Search ..260/878 polymer f ethyleneat least one other Straight chain 1 mmonoolefin and a compound selectedfrom the group consist- [56] References C'ted ing of aliphatic andcycloaliphatic polyene compounds in the UNITED STATES PATENTS presenceof a free radical catalyst in an organic solvent, and in the presence ofa seed mixture compnsmg a mixture of sand 3,151,173 9/ l 964 Nyce..260/666 monomers h Said interpolymer which has been reacted to a! l,477 9/1966 Kresge "260/878 least 15 percent conversion based on saidmonomers. 3,311,675 6/1967 Doak et a1. ....260/880 3,344,105 9/1967McDonel et al. ..260/878 28 Claims, No Drawings PLASTIC COMPOSITION ANDMETHOD OF PREPARING SAME This invention relates to the preparation ofplastic compositions, and more particularly to EPDM rubber-modifiedplastic compositions having improved properties.

A variety of high-impact or gum plastics, which are generally referredto in the art as rubber-modified plastics, and methods for theirpreparation have been proposed. However, many of the plastics preparedby the prior art processes have failed to achieve optimum properties inall respects including impact resistance, tensile strength and hardness.

Substantial improvements in preparing rubber-modified plastic have beenmade by a simple one-step process disclosed in copending application,Ser. No. 626,930, filed Mar. 30, 1967, now US. Pat. No. 3,538,191 andentitled A Process for Preparing Rubbery Plastic Compositions and theResultant Products" wherein description is made of a process forpreparing rubber-modified styrene-acrylic grafted terpolymers byinterpolymerizing a rubbery polymer, an alkenyl aromatic monomer, suchas styrene, and a acrylic monomer in the presence of an organic solvent.Rubber-modified plastics prepared by this process have been found topossess a variety of improved physical properties, such as improvedimpact resistance, as compared to rubber-modified plastics heretoforeknown.

it is an object of this invention to provide and to producerubber-modified plastics having further improved properties, and it is arelated object of the present invention to prepare improved EPDMrubber-modified plastics.

It is another object of the present invention to provide a new andimproved polymerization process for preparing EPDM rubber-modifiedplastics wherein such plastics may be prepared in a simple economicalstep by the simultaneous grafting of an EPDM rubbery polymer with aresinous copolymer.

Other objects and advantages of the invention will appear hereinafter,and it will be understood that the specific examples appearinghereinafter are provided by way of illustration and not by way oflimitation.

The concepts of the present invention reside in a copolymer resin of analkenyl aromatic monomer and an acrylic monomerwhich is grafted to anBPDM terpolymer to form an EPDM rubber-modified plastic and method forits preparation, wherein the alkenyl aromatic monomer, the acrylicmonomer and the EPDM terpolymer are interpolymerized in an organicsolvent in the presence of a free radical catalyst and in the presenceof a partially reacted seed mixture comprising the acrylic monomer, thealkenyl aromatic monomer and the terpolymer which has been reacted to atleast percent conversion based upon the monomers, and preferably to aconversion within the range of to 60 percent.

It has been found that EPDM rubber-modified plastics prepared inaccordance with the present invention have superior mechanicalproperties, such as impact resistance and melt flow properties, ascompared to plastic compositions prepared by the interpolymerization ofthe monomer and terpolymer in the absence of a seed mixture. The processof the present invention permits a heretofore unknown flexibility inpreparing plastic compositions having optimum impact resistance and meltflow properties without the sacrifice of efficiency or simplicity.

According to the preferred embodiment of the invention, the process iscarried out as a batch process wherein a portion of the recipe for abatch is placed in a suitable reactor and is reacted to at least 15percent conversion based upon the monomers present, after which thebalance of the recipe is added to the reaction vessel and the reactioncarried to completion. Thus, in this embodiment, the initial portion ofthe recipe which is partially reacted serves as the seed mixture for theoverall reaction. However, the process of the present invention can alsobe advantageously carried out in a continuous manner in accordance withanother embodiment of the invention. In a continuous process, a portionof the reaction mixture is allowed to remain in the first reactor in anintermediate stage of conversion to provide a seed mixture for the freshfeed.

The amount of the seed mixture present in the reaction mixture is notcritical. However, it is generally preferred that the seed mixtureconstitute between 15 and 75 percent by weight of the reaction mixture,and preferably between 20 and 60 percent by weight.

The initial composition of the mixture which is reacted to form the seedmixture, prior to reaction, is preferably substantially the same as thecomposition of the fresh feed with which the partially reacted seedmixture is admixed. It has been found that best results are obtainedwhen the ratio by weight between the alkenyl aromatic monomer and theacrylic monomer is at least 0.2-5 to 1, and is preferably in the rangeof l-4 to 1. In the preferred embodiment where the alkenyl aromaticmonomer and the acrylic monomer are styrene and acrylonitrile,respectively, the rubber-modified plastics of the invention achieveoptimum properties when the weight ratio between styrene andacrylonitrile is within the range of 72:38 to 78:22, or about 3:1.

The reaction mixture to be polymerized should contain about 1-50 partsby weight, and preferably 4-25 parts by weight, of the rubbery polymerfor each 99-50 parts by weight, and'preferably 96-75 parts by weight, ofthe alkenyl aromatic monomer and the acrylic monomer. It will beappreciated that the alkenyl aromatic monomer and the acrylic monomermay be one or a mixture of more than one alkenyl aromatic monomer and/oracrylic monomer respectively. The reaction mixture also contains thefree radical catalyst, preferably in an amount in the range of 0.25 to2.5 parts by weight, and more preferably 0.5 to 1.3 parts by weight ofthe free radical catalyst or initiator for each 100 parts by weight ofalkenyl aromatic monomers and acrylic monomers. Additionally, betterresults are frequently attained when the organic solvent 'content of thereaction mixture is varied between 50 percent by weight of the totalweight of the reaction mixture at the lower limit of the EPDM terpolymercontent mentioned above and 90 percent by weight thereof when the upperEPDM terpolymer range mentioned above is used. When the preferred rangeof the rubbery polymer is used, i.e., 4-25 percent by weight, then thesolvent should be present in an amount constituting -60 percent byweight of the total reaction mixture.

The alkenyl aromatic monomers which may be used in the preparation ofimproved rubber-modified plastics according to the present inventionincludes alkenyl aromatic hydrocarbons containing eight to 20 carbonatoms, and their halogenated derivatives. Specific examples of suchmonomers include styrene, chlorostyrene, alpha-alkyl styrene wherein thealkyl group contains one to eight carbon atoms, such asalpha-methylstyrene, alpha-chlorostyrene, vinyl naphthalene,alkyl-substituted vinyl naphthalene wherein the alkyl group or groupscontain one to eight carbon atoms, and halogen-substituted vinylnaphthalene. Styrene is generally the preferred alkenyl aromaticmonomer.

The acrylic monomer which may be used in the present invention are thosemonomers having a general formula:

wherein R is selected from a group consisting of hydrogen and alkylhaving one to five carbon atoms, and X is selected from a groupconsisting of:

of such monomers which have been found to be of particular use includeacrylonitrile, acrylamide, methylene or ethylene acryonitrile, acrylic,methacrylic, and ethyl-acrylic acid and the methyl, ethyl, propyl andisopropyl esters thereof. Acrylonitrile is generally the preferredacrylic monomer.

The EPDM terpolymers useful in the present invention are generally thoseelastomers prepared by the reaction of ethylene, at least one otherstraight chain alpha-monoolefin having three to 16 carbon atoms, such aspropylene, isobutylene, etc., and an aliphatic or cycloaliphatic polyenemonomer having four to 20 carbon atoms.

The polyene monomers can be conjugated dienes such as 1,3-butadiene,isoprene, chloroprene, 1,4-hexadiene, as well as a variety of otherconjugated polyenes, but are preferably non-conjugated aliphatic andcycloaliphatic dienes, such as non-conjugated hexadiene, octadiene, etc.Terpolymers prepared from the foregoing generally have relatively lowunsaturation and their preparation is known to those skilled in the art.

The preferred EPDM elastomers having relatively low unsaturation arethose prepared by the interpolymerization of a monomeric mixturecontaining 10-90 mole percent ethylene and 10-90 mole percent of atleast one other straight chain alpha-monoolefin containing three to 16carbon atoms and preferably propylene, and from 0.1 to 10 mole percentof an unsaturated bridged-ring hydrocarbon having at least onecarbon-to-carbon double bond in a bridged ring in a solution of hexaneor other organic solvent, and in the presence of a catalyst preparedfrom vanadium oxytrichloride and methyl or ethyl aluminum sesquichlorideor other suitable Ziegler catalyst. The preparation of such EPDMterpolymers is disclosed in US. Pat. Nos. 2,933,480, 3,093,620,3,093,621, 3,21 l,709, 3,ll3,l 15 and 3,300,450, the teachings of whichare incorporated herein by reference.

It is preferred that the elastomers having low unsaturation be preparedfrom a monomeric mixture containing ethylene, propylene and thepolyunsaturated bridged-ring hydrocarbon, in proportions to produce apolymer having good elastomeric properties and an unsaturation level ofat least two carbon-tcarbon double bonds per thousand carbon atoms inthe polymer. For example, the elastomer may contain chemically boundthereinmolar ratios of ethylene to propylene varying between 80:20 and20:80, and between 70:30 and 55:45 for better results. The bridged-ringhydrocarbon may be chemically bound therein in an amount to provide anunsaturation level of 2-25, and preferably about three to 16carbon-to-carbon double bonds per thousand carbon atoms in the polymer.

Examples of the bridged-ring hydrocarbons include the polyunsaturatedderivatives of bicyclo-(2,2,l)-heptane wherein at least one double bondis present in one of the bridged rings, such as dicyclopentadiene,bicyclo(2,2,1) hepta-2,5-diene, the alkylidene norbomenes, andespecially the 5-alkylidene-Z-norbornenes wherein the alkylidene groupcontains one to 20 carbon atoms and preferably one to eight carbonatoms, the alkenyl norbornenes, and especially the 5-alkenyl-2-norbornenes wherein the alkenyl group contains about three to20 carbon atoms and preferably three to carbon atoms. Other bridged-ringhydrocarbons include polyunsaturated derivatives of bicyclo-( 2,2,2)-octane as represented by bicyclo (2,2,2) octa-2,5-diene,polyunsaturated derivatives of bicyclo (3,2,1 )-octane, polyunsaturatedderivatives of bicyclo(3,3,l)-nonane, and polyunsaturated derivatives ofbicyclo-(3,2,2)-nonane. At least one double bond is present in a bridgedring of the above compounds, and at least one other double bond ispresent in a bridged ring or in a side chain. Specific examples ofbridged-ring compounds include 5- methylene-2-norbornene,5-ethylidene-2-norbornene, 5- isopropylidene-2-norbornene,di'cyclopentadiene, the methyl butenyl norbornenes such as5-(2-methyl-2-butenyl)-2-norbomene, or5-(3-methyl-2-butenyl)-2-norbornene and 5-(3,5- dimethyl-4-hexenyl)2-norbomene. The elastomers prepared from ethylene, at least onemonoolefin containing three to 16 carbon atoms, and the5-alkylidene-2-norbomenes, wherein the alkylidene group contains one to20 and preferably one to eight carbon atoms, produce novelrubber-modified plastics which have exceptional properties. Theelastomer prepared from 5-ethylidene-2-norbornene is much preferred asit has outstanding properties and produces many unusual and unexpectedresults when used as the elastomer in the plastic compositions of theinvention. As a result, this elastomer is in a class by itself.

In instances where an elastomer is employed which has no unsaturation orvery little unsaturation, then it is often desirable to prepare ahydroperoxide thereof by oxidation prior to the polymerization step ofthe present invention. The oxidation may be in accordance with prior artpractice, such as by heating a solution of the elastomer in the presenceof molecular oxygen and an organic peroxide or hydroperoxide as acatalyst. In one suitable method, the elastomer is dissolved in amixture of benzene and hexane, and benzoyl peroxide is added as acatalyst for the oxidation. The reaction vessel is pressurized to 50 psiwith oxygen and maintained at 70 C. for 0.5 to 8 hours. Oxidation canalso be affected without a free radical catalyst by reacting for 2 to 10hours. The resin monomers are added to the solution of the oxidizedrubber, with or without adding an additional free radical catalyst, andpolymerized to form a rubber-modified plastic according to the presentinvention. The hydroperoxide groups may alone act as the free radicalcatalyst for the monomer polymerization. It is understood that theelastomer may be oxidized to form hydroperoxide groups thereon wheneverthere is difficulty in reacting the elastomer substrate with the graftmonomers in the desired amounts to thereby achieve greater ease ofgrafting.

A wide variety of free radical polymerization catalysts may be employed,including those used in the prior art processes for preparing highimpact polystyrene and styreneacrylonitrile plastics. In some instances,the hydroperoxide groups that are formed by oxidation of the rubberycomponent may act as the free radical catalyst. Examples of free radicalpolymerization catalysts include the organic peroxides such as benzoylperoxide, lauroyl peroxide, propionyl peroxide, 2,4-dichlorobenzoylperoxide, acetyl peroxide, tertiary butyl hydroperoxide, tertiary butylperbenzoate, tertiary butyl peroxyisobutyrate, and dicumylperoxide.Mixtures of one or more peroxides may be employed. Additionally,mixtures of one or more peroxides with azo-bisdiisobutyronitrile givebetter results in some instances, and especially where a less activecatalyst is effective. For example, when using the highly unsaturateddiene rubbers, or rubbers of low or high unsaturation that have beensubjected to an oxidation step to form hydroperoxide groups thereon,then a less active free radical catalyst should be used for optimumresults. The catalyst mixture may contain 25-75 percent and preferablyabout 50 percent by weight of the azo-bisdiisobutyronitrile, and 75-25percent, and preferably about 50 percent by weight, of one or more ofthe above organic peroxides. In instances where an unoxidized elastomeris used having a low degree of unsaturation, then it is desirable toemploy a highly active free radical initiator, e.g., a prior artinitiator which is known to abstract hydrogen from the elastomer andrapidly catalyze the graft reaction. Many examples of such highly activefree radical initiators are known, such as benzoyl peroxide.

The organic solvent that is selected must be a solvent for the rubberypolymer. Examples of suitable solvents include aromatic hydrocarbonssuch as benzene, benzene substituted with one or more alkyl groupscontaining two to four carbon atoms such as toluene, dimethylbenzene,xylene and their higher homologs, naphthalene, naphthalene substitutedwith one or more alkyl groups containing one to four carbon atoms suchas alpha-methyl or beta-methyl naphthalene and their higher homologs,paraffin and cycloparaffin hydrocarbons containing five to 15 carbonatoms, and preferably six to 10 carbon atoms, such as pentane, n-hexane,3-methylpentane, 2- methylpentane, 2,2- and 2,4-dimethylpentane,heptane, cyclopentane, cyclohexane, and alkyl substituted cyclopentanesand cyclohexanes wherein the alkyl group or groups contain one to fourcarbon atoms, including methyl cyclopentane, methyl cyclohexane andtheir homologs. The

halogenated derivatives of the above solvents may be employed, andespecially the chlorine and bromine derivatives. Chlorobenzene is veryuseful as a solvent.

Mixtures containing two or more of the foregoing solvents may be used,and are preferred in many instances. Examples of solvent mixtures whichgive unusually good results include an aromatic component such asbenzene and/or toluene, and a paraffin or cycloparaffin hydrocarboncomponent containing six through eight carbon atoms such as n-hexane,B-methylpentane, Z-methylpentane, n-heptane, methyl hexanes, n-octane,methyl octanes methylcyclopentane, and/orcyclohexane.

Usually better results are obtained when the above solvent mixturescontain about 40-60 percent by weight of the aromatic solvent component,and about 60-40 percent by weight of the paraffin or cycloparaffinhydrocarbon component. Best results are usually obtained when about 50%by weight of each component is present.

It will be understood by those skilled in the art that in the practiceof the present invention there is a tendency for the final conversion tobe somewhat lower than that of a batch process because of the dilutionof the partially reacted seed mixture with fresh unreacted feed,particularly in those instances where the seed mixture constitutesgreater than 50 percent by weight of the reaction mixture. Thisreduction in conversion can be advantageously compensated for by theincremental addition of a non-aromatic or aliphatic solvent to thereaction mixture after the reaction is commenced. The non-aromaticsolvents-found most suitable for this purpose are the paraffin andcycloparaffin solvents disclosed above, with the most preferred solventbeing hexane.

Without limiting the invention as to theory, it is believed thatnon-aromatic solvents, such as hexane, are poorer solvents for the graftterpolymer product formed by the process of the invention, and thusthere is a tendency for the product to precipitate out of the reactionmixture as it is formed, thereby driving the reaction further toward 100percent conversion. The use of this technique in the process of theinvention has further advantages in that there are less of the unreactedmonomers to be separated from the final product, and the coagulationproceeds more smoothly to provide a product in the form of a finepowder.

The amount of the solvent added to the reaction mixture is not critical,and is preferably an amount up to 50 percent by weight of the totalamount of solvent present in the reaction mixture prior to the additionof the non-aromatic solvent.

When a non-aromatic solvent is added incrementally to the reactionmixture in accordance with this concept, the total amount of the solventand the relative proportions of the aromatic and non-aromatic solvents,when a mixture of such solvents is used, initially present in thereaction mixture prior to the addition of the non-aromatic solventremain essetially unchanged from the amounts disclosed above. It will beappreciated that the aliphatic solvent may be added in one or moreincrements.

The time of making the addition or additions depends primarily upon thereaction temperature, and generally falls between one-seventh andsix-seventh of the total reaction time required to achieve at least 90percent conversion. At higher reaction temperatures, it is generallydesirable that the addition be made later during the course of reaction,and multiple additions are of preferred at such temperatures, includingas many as 5 incremental additions during the course of the reaction.

The temperature of the polymerizationreaction may vary over wide ranges.For example, reaction temperatures within the range of about 40-l50 C.,and preferably within the range of about 60?85 C. are generallysatisfactory. It has been found that lower temperatures within theseranges generally result in rubber-modified plastics having increasedimpact resistance, whereas higher temperatures within the disclosedranges generally result in a product having increased melt flowproperties. In order to achieve optimum impact and melt flow propertiesin the product, it is particularly preferred to operate within thenarrow range of 70-80 C. In general, use is made of a reactiontemperature such that the free radical initiator should have a half lifeof 4-l 5 hours. The reaction is continued for a sufficient period oftime to insure the desired percent conversion of the monomers present inthe reaction mixture. The reaction time will vary somewhat with thespecific catalyst, solvent system, rubbery polymer, monomers andreaction temperature which are employed. However, reaction temperatureswithin the range of 4-24 hours are generally satisfactory. In any event,the reaction is preferably continued until at least 60 percent by weightof the monomeric material present in the reaction mixture has beenconverted to polymer, and preferably until a conversion within the rangeof -95 percent by weight is reached.

The reaction mixture also may contain a cross-linking agent, i.e., acompound containing at least two reactive sites such as two or moreethylenic double bonds. Examples of cross-linking agents aredivinylbenzene, divinyl ether of diethylene glycol, triallylcyanurate,and l,3-butylene-' dimethacrylate. The cross-linking agent may be addedin an amount of, for example, 0.005-l.0 parts by weight, and preferablyabout 0.01 to 0.5 parts by weight, per parts by weight of the monomericmaterial to be polymerized. Still other types of cross-linking agentsmay be employed as it is only necessary that it have two or morereactive sites under the conditions of the polymerization.

The reaction mixture may be agitated during the polymerization butvigorous agitation is not necessary. As the polymerization proceeds, theresinous polymer that is formed generally precipitates in a finelydispersed form and remains suspended in the reaction mixture. The EPDMterpolymer generally remains dissolved in the solution after it has beengrafted with the resin-forming monomers. Thus, the polymerizationreaction simultaneously produces a resinous terpolymer of the alkenylaromatic and acrylic monomers and the EPDM terpolymers grafted with theresin-forming alkenyl aromatic and acrylic monomers. As a result, at theend of the polymerization the reaction mixture contains all thecomponents which are needed for a high impact plastic composition, andit is only necessary to recover the products of the polymerizationtherefrom.

The plastic composition may be recovered from the reaction mixture bycoagulation with a lower aldohol such as methyl, ethyl or isopropylalcohol, or by flashing off the solvent. When the product is recoveredby flashing the solvent, preferably the reaction mixture is passed intoa vessel containing boiling water. Steam is supplied to the vessel andthe solvent evaporates and is removed overhead as a vapor, together withany free monomer content. The plastic product is recovered as a solid inparticulate form, and it may be dewatered, washed in water to removewater-soluble impurities, and air dried or, preferably dried at anelevated temperature, such as at a temperature within the range of 50l50C. until the water content is removed. Fluidized bed drying at 50-l50 C.also may be used in most instances with good results. The dried plasticcomposition may be pelletized or formed into other desirable shapessuitable for marketing.

Prior art antioxidants, processing aids, and other compoundingingredients and aids may be added at any convenient point in theprocess. Inasmuch as these ingredients are soluble or dispersible in theorganic solvent, they may be added to the polymerization mixture priorto recovery of the product. Examples of suitable antioxidants includephosphited polyalkyl polyphenols and tri(mixed monononyl-dinonyl) phenylphosphite. Examples of processing aids are mineral oils and the saltsand esters of higher fatty acids. When desired, coloring agents may beadded to produce colored resins. The

coloring pigments of the prior art are suitable for this purpose.

The high impact plastic compositions prepared by the process of thepresent invention have superior physical properties, and particularlysuperior impact resistance, as compared to similar products preparedfrom EPDM terpolymers which have not been, prior to polymerization,oil-extended. Additionally, by using the preferred EPDM terpolymershaving low unsaturation, particularly the terpolymers of ethylene,propylene and -alkylidene-2-norbornene, even better physical propertiesmay be obtained. The novel plastic composition of the present inventioncomprises (A) a resinous copolymer of an alkenyl aromatic monomer and anacrylic monomer and (B) a graft interpolymer (1) an elastomericinterpolymer of ethylene, at least one other alpha-monoolefin and analiphatic or cycloaliphatic polyene, (2) an alkenyl aromatic monomer and(3) an acrylic monomer.

As indicated, the preferred polyenes are the 5-alkylidene-2-norbornenes, wherein the alkylidene group contains one to eight carbonatoms, with the preferred species being S-ethylidene-Z-norbornene.

Reference is now made to the following examples which are illustrativeof the principal concepts of the present invention.

EXAMPLE 1 This example illustrates the unexpected improvements in theproperties of EPDM rubber-modified plastics prepared in accordance withthe concepts of the present invention.

The EPDM terpolymer used in this example is an interpolymer of ethylene,propylene and S-ethylidene-Z-norbornene, which contains approximatelyequal weights of ethylene and propylene and sufficientS-ethylidene-Z-norbornene to provide an unsaturation level of 8.7carbon-tocarbon double bonds per 1,000 carbon atoms and which has aMooney value of 66 (ML-4 A recipe. is prepared from the aboveterpolymer, styrene and acrylonitrile which has the followingcomposition:

Solvent (benzene and hexane in equal parts by weight) l400 Parts byWeight Styrene 450 Parts by Weight Acrylonitrile l50 Parts by WeightEPDM 82 Parts by Weight Benzoyl peroxide 6 Parts by Weight ln Run l, theentire recipe is charged to a reactor equipped with a stirrer which isheated to and maintained at a temperature of 70 C. The reaction iscarried out with agitation to final conversion (90 to 99 percent basedupon the styrene and acrylonitrile monomers) without interruption. Thetotal time for reaction is 12 hours, after which the resulting productis precipitated from the reaction mixture by the addition of alcohol.The solid plastic polymer is then dewatered, washed in water to removewater-soluble impurities, died and tested for lzod impact resistance andto determine the melt flow index in g./ minutes. The results of thesetests are shown in Table I.

In Run 2, 50 percent by weight of the recipe is charged to the reactorused in Run 1 which is maintained at 78 C., and is reacted to percentconversion. Thereafter, the reaction is interrupted and the remaining 50percent by the recipe is added to the reactor, and the entire mixture isreacted to final conversion (90 to 99 percent). The product is testedfor impact resistance and melt flow properties, the results of which areshown in Table l.

The procedure shown in Run 2 is employed in Runs 3, 4, 5 and 6, exceptthat the amount of the recipe added to the seed mixture and theconversion of the seed mixture of the time the balance of the recipe isadded are as shown in Table I.

It will be apparent from the foregoing that the concepts of the presentinvention provide a plastic composition which has superior impactresistance and melt flow index. Thus, in Run 1 where the entire batchwas reacted to final conversion without interruption, the impactresistance and melt flow index of the polymers produced was lower thanthat for polymers produced wherein the reaction mixture contained lessthan 75 percent by weight of the seed mixture. Run 2 illustrates thatbetter flow properties are achieved in polymers prepared at highertemperatures within the disclosed ranges, whereas Run 3 demonstratesthat improved impact resistance is achieved by polymerization at lowertemperatures.

EXAMPLE 2 The terpolymer used in Example 1 is dissolved in a mixture ofequal parts by weight hexane and benzene, and styrene,

acrylonitrile and catalyst are added to form the following composition.

Parts by weight Solvent 1400 Styrene 450 Acrylonitrile EPDM terpolymer 1l5 Benzoyl peroxide 6 product are shown in Table ll.

TABLE II Amount of Conversion recipe added of seed at Melt to seed timeof Temp. lzod Flow Run mixture addition C. Impact lndex The foregoinglikewise demonstrates the flexibility of the method of the presentinventionin that it shows that at higher temperatures within thepreferred range, a plastic composition is produced which has asignificantly greater melt flow index without a large change in theimpact strength.

EXAMPLE 3 The terpolymer used in Examples l and 2 is dissolved in asolvent comprising equal weights of toluene and hexane, and theresulting solution is mixed with alpha-methyl styrene, acrylic acid anda catalyst.

50 percent by the mixture is charged to a Sutherland Reactor equippedwith a stirrer, and is carried to 35 percent conversion based upon thealpha-methyl styrene present. Thereafter, the remaining 50 percent ofthe batch isadded to the reactor, and the entire mixture is carried tofinal conversion at a temperature of 75 C.

The product is spearated in the manner shown in Example I, and is foundto have an Izod impact strength of 4.91 ft.- lblinanotch and a melt flowof 0.89 g/lO minutes.

EXAMPLE 4 In this example the EPDM terpolymer is an interpolymer ofethylene, propylene and dicyclopentadiene having an ethylene-propyleneweight ratio of 58:42 and containing 3 percent by weightdicyclopentadiene.

The terpolymer is dissolved in a hexane-benzene solvent mixture andmixed with alpha-chlorostyrcne and methyl acrylate and dicumyl peroxidecatalyst. 60 percent of the batch is reacted for 5 hours to achieve 45percent conversion based upon the alpha-chlorostyrene, at which time theremaining portion of the batch is added.

The product separated at final conversion of the entire mixture is foundto possess improved impact resistance and melt flow properties.

EXAMPLE This example illustrates the concepts of present invention asapplied to a continuous process. The terpolymer of Example 1 isformulated into a composition of the following materials.

Parts by Weight Benzene 780 Hexane 780 EPDM terpolymer I08 Styrene 622Acrylonitrile I66 Benzoyl peroxide 7.88

The reaction mixture is continuously fed to a reaction system comprisingthree reaction vessels of the type used in Example 1 which are connectedin series at a rate of 25.0 ml/mi. Reactors l and 3 are maintained at 74C. while reactor 2 is maintained at 70 C.

Since only a portion of the reaction medium is continuously beingdisplaced from the first reactor to the next, material remains in thefirst reactor in intermediate conversion to provide the seed for theingredients fed into the first reactor to achieve a steady state. Thereaction mixture in reactor 3 is continuously carried to finalconversion, resulting in a product having a melt flow of'0.52 g/l0 min.and an Izod impact of 4.97 ft.-lb/in.-notch.

EXAMPLE 6 This example illustrates the concept of the present inventionwherein an aliphatic solvent is added to a reaction mixture containing asolvent mixture of an aromatic solvent and an aliphatic solvent.

A batch comprising the terpolymer of Example 1, styrene, acrylonitrileand catalyst is prepared in a benzene-hexane solvent mixture having thefollowing composition:

Benzene 770 g. Hexane 630 g. Styrene 450 g. EPDM terpolymer 82 g.Acrylonitrile 150 g. Benzoyl peroxide 6 g.

final ratio is 45/55. The product is found to have an lzod impact of5.20 ft.-lb/in.-notch and a melt flow index of l.2l g/ l 0 min.

EXAMPLE 7 The composition and procedure of Example 6 is employed in thisexample, except that the hexane is added in one increment after thereaction has proceeded for 6 hours at 75 C.

The resulting product is found to have an Izod impact strength of 5.67ft.-lb./in.-notch and a melt fiow index of 0.40.

EXAMPLE 8 The terpolymer used in this example is a terpolymer ofapproximately equal parts by weight of ethylene and propylene andsufficient l,4-hexadiene to provide a rubbery terpolymer containingthree carbon-to-carbon double bonds per 1,000 carbon atoms.

The terpolymer is dissolved in a solvent comprising equal weights oftoluene and hexane, and the resulting solution is admixed withalpha-methyl styrene, acrylonitrile and a catalyst.

55 percent of the reaction mixture is charged to a reaction vesselequipped with a stirrer, and is carried to about 40 percent conversionbased upon the monomers present. Thereafter, the remaining 40 percent ofthe reaction batch is added to the vessel, and the entire mixture iscarried to final conversion of 92 percent at a temperature of 77 C.

The rubber-modified plastic product is separated from the reactionmixture, and is found to have improved impact resistance and melt flowproperties.

It will be apparent from the foregoing that we have provided a new andimproved process for preparing rubber-modified plastics having furtherimproved properties as compared to those rubber-modified plasticsheretofore known. The process of the present invention permits a greatdeal of flexibility in preparing plastic compositions having theforegoing improved properties without the sacrifice of efficiency andeconomy.

It will be understood that various changes may be made in the details offormulation and operation without departing from the spirit of theinvention, especially as defined in the following claims.

We claim:

1. A plastic composition formed by the reaction of 99 to 50 parts byweight of an alkenyl aromatic monomer and an acrylic monomer having theformula wherein R is selected from the group consisting of hydrogen andC to C alkyl and X is selected from the group consisting of wherein R isC to C, alkyl wherein the weight ratio between the alkenyl aromaticmonomer and the acrylic monomer is within the range of 0.2 to 5, and lto 50 parts by weight of an elastomeric interpolymer of ethylene, atleast one straight chain alpha-monoolefin containing three to 16 carbonatoms and a compound selected from the group consisting of aliphatic andcycloaliphatic polyenes in the presence of a free radical catalyst in aninert organic solvent selected from the group consisting of aromatichydrocarbons, their alkyland halogen-substituted derivatives, aliphatichydrocarbons and their halogen-substituted derivatives and mixturesthereof, and in the presence of 15-75 percent by weight of a seedmixture consisting essentially of said monomers and said interpolymerwhich have been reacted to 15-75 percent conversion based on saidmonomers.

2. A composition as defined in claim 1 wherein said seed mixture hasbeen reacted to a conversion within the range of 20-60 percent based onsaid monomers.

3. A composition as defined in claim 1 wherein said alkenyl aromaticmonomer and said acrylic monomer are present in a weight ratio in therange of l-4 to 1.

4. A composition as defined in claim 1 wherein said alkenyl aromaticmonomer is styrene and said acrylic monomer acrylonitrile.

5. A composition as defined in claim 1 wherein the weight ratio betweenthe styrene and the acrylonitrile is within the range of 72:28 to 78:22.

6. A composition as defined in claim 1 wherein said alphamonoolefin ispropylene.

7. A composition as defined in claim 1 wherein said polyene compound isa polyunsaturated bridged-ring hydrocarbon having at least onecarbon-to-carbon in a bridged ring.

8. A composition as defined in claim 1 wherein said polyene compound isa polyunsaturated derivative of a compound selected from the groupconsisting of bicyclo-(2,2,l )-heptane, bicyclo-(2,2,2)-octane,bicyclo-(3,2,1)-octane, bicyclo- (3,3 ,1 )-nonane and bicyclo( 3,2,2)-nonane.

9. A composition as defined in claim 1 wherein said polyene compound isa 5-alkylidene-2-norbornene.

10. A composition as defined in claim 1 wherein said elastomericterpolymer is a terpolymer of ethylene, propylene and5-ethylidene-2-norbornene.

11. A composition as defined in claim 1 wherein said seed mixtureconstitutes from 20-60 percent by weight of the reaction mixture.

12. In a process for preparing improved plastic compositions wherein 99to 50 parts by weight of an alkenyl aromatic monomer and an acrylicmonomer having the formula wherein R is selected from the groupconsisting of hydrogen and C to C alkyl and X is selected from the groupconsisting of wherein R is C to C alkyl wherein the weight ratio betweenthe alkenyl aromatic monomer and the acrylic monomer is within the rangeof 0.2 to 5, and 1 to 50 parts by weight of an elastomeric interpolymerof ethylene, at least one straight chain alpha-monool'efin containingthree to 16 carbon atoms and a compound selected from the groupconsisting of aliphatic and cycloaliphatic polyenes are reacted in aninert organic solvent selected from the group consisting of aromatichydrocarbons, their alkyland halogen-substituted derivatives, aliphatichydrocarbons and their halogen-substituted derivatives and mixturesthereof in the presence of a free radical catalyst, the improvementcomprising reacting said monomers and said interpolymer in the presenceof -75 percent by weight of a seed 'mixture comprising a mixture of saidmonomers and said interpolymer which has been reacted to 15-75 percentconversion based upon said monomers.

13. A process as defined in claim 12 wherein said seed mixture has beenreacted to a conversion within the range of -60 percent based upon saidmonomers.

14. A process as defined in claim 12 wherein said seed mixtureconstitutes from 15-75 percent by weight of the reaction mixture.

15. A process as defined in claim 12 wherein said seed mixtureconstitutes from 20-60 percent by weight of the reaction mixture.

16. A process as defined in claim 12 wherein said alphamonoolefin ispropylene.

17. A process as defined in claim 12 wherein said polyene compound is apolyunsaturated bridged-ring compound having at least onecarbon-to-carbon in a bridged ring.

18. A process as defined in claim 12 wherein said polyene coumpound is apolyunsaturated derivative of a compound selected from the groupconsisting of bicycle-(2,2,1 )-heptane, bicyclo-(2,2,2)-octane,bicyclo-(3,2,l)-octane, bicyclo- (3,3,l )-nonane andbicyclo(3,2,2)-nonane.

19. A process as defined in claim 12 wherein said polyene compound isS-alkylidine-2-norbomene.

20. A process as defined in claim 12 wherein said terpolymer is aterpolymer of ethylene, propylene, and S-ethylidene-2-norbornene.

21. A process as defined in claim 12 wherein said alkenyl aromaticmonomer is styrene and said acrylic monomer is acrylonitrile.

22. A process as defined in claim 12 wherein the weight ratio betweenthe alkenyl aromatic monomer and acrylic monomer is 14 to 1.

23. A process as defined in claim 12 wherein the reaction mixturecontains 4-25 parts by weight of said terpolymer for each 96-75 parts byweight alkenyl aromatic monomer and said acrylic monomer.

24. A process as defined in claim 12 wherein said solvent is a mixtureof aromatic and aliphatic solvent.

25. A process as defined in claim 12 wherein the reaction is carried outat a temperature within the range of 401 50 C.

26. A process as defined in claim 12 wherein an aliphatic solvent isadded to the reaction mixture in at least one increment during thereaction.

27. A process as defined in claim 26 wherein said increment is added ata time falling within one-seventh and six-seventh of the total reactiontime required to achieve at least percent conversion based on saidmonomers.

28. A process as defined in claim 12 wherein the reaction is carried outat a temperature within the range of 7080C.

UNETED STAT ES PATENT OFFICE (IETWMIATE @F CGREC'HGN Patent No. 3 I 608Dated June 20, 1972 Inventor) Curtis L. Meredith et al.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 2, line 20, change "72:38" to 72:28

Signed and sealed this 17th day of October 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents FORM P0-1050 (19-69) USCOMM-DC 60376-P69 h US. GOVERNMENTPRINTING OFFICE: 959 0356334

2. A composition as defined in claim 1 wherein said seed mixture hasbeen reacted to a conversion within the range of 20-60 percent based onsaid monomers.
 3. A composition as defined in claim 1 wherein saidalkenyl aromatic monomer and said acrylic monomer are present in aweight ratio in the range of 1-4 to
 1. 4. A composition as defined inclaim 1 wherein said alkenyl aromatic monomer is styrene and saidacrylic monomer acrylonitrile.
 5. A composition as defined in claim 1wherein the weight ratio between the styrene and the acrylonitrile iswithin the range of 72:28 to 78:22.
 6. A composition as defined in claim1 wherein said alpha-monoolefin is propylene.
 7. A composition asdefined in claim 1 wherein said polyene compound is a polyunsaturatedbridged-ring hydrocarbon having at least one carbon-to-carbon in abridged ring.
 8. A composition as defined in claim 1 wherein saidpolyene compound is a polyunsaturated derivative of a compound selectedfrom the group consisting of bicyclo-(2,2,1)-heptane, bicyclo-(2,2,2)-octane, bicyclo-(3,2,1)-octane, bicyclo-(3,3,1)-nonane andbicyclo(3,2,2)-nonane.
 9. A composition as defined in claim 1 whereinsaid polyene compound is a 5-alkylidene-2-norbornene.
 10. A compositionas defined in claim 1 wherein said elastomeric terpolymer is aterpolymer of ethylene, propylene and 5-ethylidene-2-norbornene.
 11. Acomposition as defined in claim 1 wherein said seed mixture constitutesfrom 20-60 percent by weight of the reaction mixture.
 12. In a processfor preparing improved plastic compositions wherein 99 to 50 parts byweight of an alkenyl aromatic monomer and an acrylic monomer having theformula wherein R is selected from the group consisting of hydrogen andC1 to C5 alkyl and X is selected from the group consisting of whereinR'' is C1 to C9 alkyl wherein the weight ratio between the alkenylaromatic monomer and the acrylic monomer is within the range of 0.2 to5, and 1 to 50 parts by weight of an elastomeric interpolymer ofethylene, at least one straight chain alpha-monoolefin containing threeto 16 carbon atoms and a compound selected from the group consisting ofaliphatic and cycloaliphatic polyenes are reacted in an inert organicsolvent selected from the group consisting of aromatic hydrocarbons,their alkyl- and halogen-substituted derivatives, aliphatic hydrocarbonsand their halogen-substituted derivatives and mixtures thereof in thepresence of a free radical catalyst, the improvement comprising reactingsaid monomers and said interpolymer in the presence of 15-75 percent byweight of a seed mixture comprising a mixture of said monomers and saidinterpolymer which has been reacted to 15-75 percent conversion basedupon said monomers.
 13. A process as defined in claim 12 wherein saidseed mixture has been reacted to a conversion within the range of 20-60percent based upon said monomers.
 14. A process as defined in claim 12wherein said seed mixture constitutes from 15-75 percent by weight ofthe reaction mixture.
 15. A process as defined in claim 12 wherein saidseed mixture constitutes from 20-60 percent by weight of the reactionmixture.
 16. A process as defined in claim 12 wherein saidalpha-monoolefin is propylene.
 17. A process as defined In claim 12wherein said polyene compound is a polyunsaturated bridged-ring compoundhaving at least one carbon-to-carbon in a bridged ring.
 18. A process asdefined in claim 12 wherein said polyene coumpound is a polyunsaturatedderivative of a compound selected from the group consisting ofbicyclo-(2,2,1)-heptane, bicyclo-(2, 2,2)-octane,bicyclo-(3,2,1)-octane, bicyclo-(3,3,1)-nonane andbicyclo(3,2,2)-nonane.
 19. A process as defined in claim 12 wherein saidpolyene compound is 5-alkylidine-2-norbornene.
 20. A process as definedin claim 12 wherein said terpolymer is a terpolymer of ethylene,propylene, and 5-ethylidene-2-norbornene.
 21. A process as defined inclaim 12 wherein said alkenyl aromatic monomer is styrene and saidacrylic monomer is acrylonitrile.
 22. A process as defined in claim 12wherein the weight ratio between the alkenyl aromatic monomer andacrylic monomer is 1-4 to
 1. 23. A process as defined in claim 12wherein the reaction mixture contains 4-25 parts by weight of saidterpolymer for each 96-75 parts by weight alkenyl aromatic monomer andsaid acrylic monomer.
 24. A process as defined in claim 12 wherein saidsolvent is a mixture of aromatic and aliphatic solvent.
 25. A process asdefined in claim 12 wherein the reaction is carried out at a temperaturewithin the range of 40*-150* C.
 26. A process as defined in claim 12wherein an aliphatic solvent is added to the reaction mixture in atleast one increment during the reaction.
 27. A process as defined inclaim 26 wherein said increment is added at a time falling withinone-seventh and six-sevenths of the total reaction time required toachieve at least 90 percent conversion based on said monomers.
 28. Aprocess as defined in claim 12 wherein the reaction is carried out at atemperature within the range of 70*-80* C.